Polymerization of olefins



Patented June 18, 1940 UNITED STATES POLYMERIZATION F OLEFINS Donald R.Stevens, Swissvale, and William A.

' Gruse, Wilkinsburg, Pa., assignors to Gulf Research & DevelopmentCompany, Wilmington, Del., a corporation ofDelaware No Drawing.Application October 22, 1936, Serial No. 107,102

13 Claims.

This invention relates to polymerization of olefin s, and it comprises amethod of treating olefin1c gases for the production of low-boilingliquid polymers useful as a motor fuel, which comprises 5 bringing theolefinic gases into contact with a strong acid such as strong sulfuricacid or benzene sulfonic acid, in the presence of boric acid, the boricacid acting as a modifying or mitigatmg agent to restrain undesirablenon-polymerizingactivities of the acid and to regulate and control thedegree of polymerization of the olefins; all as more fully hereinafterset forth and as claimed.

Considerable attention has been paid in recent years to thepolymerization of olefinic gases for the production of low-boilingliquid polymers useful as motor fuel. Various thermal and catalyticprocesses have been proposed and used. Of the catalytic processes, onewhich has attained some m success relies upon the use of phosphoric acidas a polymerizing catalyst. Commercial sirupy phosphoric acid(orthophosphoric acid) can be used to give a fair yield ofpolymers fromolefinic gases, when properly employed, and the products 35 obtained arelargely useful as motor fuel. However, the process is subject to somedisadvantages; phosphoric acid is relatively expensive and at hightemperatures the ortho acid tends to go over to dehydrated forms (pyroand meta acids) in an irregular way with irregular results. Sometimesvolatile esters are produced.

Sulfuric acid is free from the disadvantages noted and is much cheaperthan phosphoric acid, but it is a stronger acid and this fact imposessome restriction upon its use. If high-strength acid is used, it tendsat elevated temperatures to react with the hydrocarbons undergoingtreatment, forming sulfur dioxide and carbonization products. Strongsulfuric acid also tends to have too strong a polymerization eflect,producing polymers which are too high boiling to be used for gasolinemotor fuel. It cannot be re-used. 0n the other hand, dilute sulfuricacid is largely restricted in its polymerization efiect to iso- 45'butylene. Thus iso-butylene may be polymerized to the dimer(di-isobutylene) and the trimer (tri-iso-butylene) by absorption ofiso-butylene in 60 to 65 percent H2804, the. acid subsequently adjustedin acidity and warmed to separate polymerized products, as disclosed inour copending application Serial No. 54,336, filed December 1935, saidmethod comprising a modification of the well known Butlerow methoddescribedin the literature as far back as 187 Our present inventioncomprises a process of polymerizing gaseous oleiins in which thedisadvantages of the strong-acid processes mentioned hereinabove areovercome. According to our invention, the polymerizing agent comprises,a mixture of a strong acid, such as strong sulfuric acid, benzenesulfonic acid, toluene sulfonic acid, phenol sulfonic acid, naphthalenesulfonic acid or the like, with boric acid. The boric acid hasamodifying or mitigating effect upon the activity of the strong acid,not only reducing or eliminating the tendency toward undesirable sidereactions, but controlling the extent of polymerization, so that theresultant polymers are more volatile than would otherwise be the case,and are henoemore suitable as motor fueli When a high yield of gasolinepolymers is desired, the process is carried out by subjecting olefinicgases containing butylenes or propylene or both to contact with themixture of strong acid and mitigating agent at a suitable elevatedtemperature preferably one sumciently high to permit volatilization andremoval of polymers as they are formed, the polymers being subsequentlycondensed. On the other hand, when a high yield of polymers heavier thangasoline is desired, as in the manufacture of a safety fuel of lowvolatility, lower temperatures are employed; in this case the liquidpolymers may not entirely voiatilize and may be separated from thecatalyst in liquid form. 1

It is advantageous to distribute the mixtureof strong acid andmitigating-agent upon a suitable inert carrier such as pumice, fullersearth or the like, for contact purposes.

The strength of the acid employed may vary considerably in accordancewith the temperature employed and the results desired. Ordinarily weprefer to use to per cent sulfuric acid. However, somewhat more diluteacid, for example down to 65 per cent sulfuric acid, may be employed athigh temperatures if desired, although a diminution in the extent ofpolymerization results, especially with regard to relatively diluteolefinic gases. On the other hand, 90 to per cent acid may be employed,especially with relatively dilute oleflnic gases, but the polymersformed tend to be somewhat less volatile; the use of 90 to 100 per centsulfuric acid is however useful for the manufacture of safety fuel andsimilar products of relatively low volatility.

The temperatures employed will depend largely upon the concentration ofthe acid and the olefinic starting material, but in general should besufficient to permit vaporization and removal of the polymers or adesired fraction thereof. With all) the preferred to per cent sulfuricacid, the temperatures may run as high as 200 C., while with thesulfonic acids temperatures not exceeding 150 C. are desirable in orderto reduce decomposition tendencies. High operating temperatures areadvisable when it is desired to obtain a relatively volatile product; i.e., one containing a high ratio of polymers boiling below 140 C. Contacttimes of from one to five minutes are preferred.

The pressures employed in the operation may run as high as 500 poundsper square inch, the higher pressures being especially useful whenrelatively dilute olefinic gases are employed as starting material, butordinarily the preferred pressure range is from to 300 pounds per squareinch.

The amount of boric acid used will in general run from 10 per cent to 25per cent by weight of the strong acid, but high proportions of boricacid may require the use of relatively high temperatures of operation.We have obtained the most advantageous results by using boric acid in anamount equal to from 15 to 20 per cent by weight of the strong acid,this range of proportions being sufficient to give the desiredmitigating action without any undesirable effect.

In a practical embodiment of the invention directed toward theproduction of polymers boiling within the range of ordinary gasoline,1000 parts by weight of a refinery butane out were contacted for fiveminutes with 1270 parts by weight of 90 per cent sulfuric acid, admixedwith 20 per cent by weight of boric acid. The hydrocarbon phase whichseparated off above the acid layer was freed of butane by releasingpressure and weathering, and was subsequently alkali washed andfractionally distilled. The product, amounting to 50 per cent by weightof the unsaturated content of the original gases, had the followingdistil lation characteristics:

Per cent Below C 27 140 to 190 C 52 Above 190 C 21 Only a slighttendency towards side reactions was observed in the above example, asindicated by the absence of the odor of S02 and the light color of theacid after use.

By way of comparison with the above results, the use of 90 per centsulfuric acid, without boric acid, gave a polymer having the followingdistillation characteristics:

Per cent Below 140 C 9.5 140 to 190 C 28.5 Above 190 C 62' capable ofbeing employed over-long periods in continuousjoperation.

Both of the runs above noted above were carried out at a temperature of70 F. and under only such pressure as developed in a closed system.:Naturally, as would be expected, the total yield of liquid polymer perpass is somewhat lower when boric acid is employed as a mitigating agentthan when sulfurioacid of the same strength is employed alone, but thisis due primarily to the formation in the latter instance of polymerswhich are too high boiling to be desirable for use, as gasoline motorfuel; the total yield of gasolinelike polymers is higher inthe case ofthe mitigated acid than in the case of the strong acid alone.

In the above runs, the refinery gas employed was a so-called butane cut"containing 32 per cent iso-butylene, 32 per cent l-butene and 2- butene,5.7 per cent of C3 hydrocarbons, and the balance consisting of normaland iso-butane. Our experiments have shown that our process polymerizesnot only iso-butylene but also l-butene and Z-butene, as well aspropylene. Ethylene is less readily polymerized.

In another embodiment of our invention, isobutylene was contacted in onerun with benzene sulfonic acid and in a second run with a mixture of 100parts by weight of benzene sulfonic acid and 15 parts by weight of boricacid, the temperature in each case being F. In the case of benzenesulfonic acid alone, there was considerable evolution of S02, evidenceof side reactions and decomposition; this effect was hardly noticeablein the case of the mitigated acid. The polymers recovered in the secondrun were largely within the gasoline boiling-point range, while thoseresulting from the use of the unmitigated acid contained a much largerproportion of material heavier than gasoline. The total yield in thesecond run was lower, but by repeating the contact in a series ofoperations, it is possible to obtain a higher yield of low-boilinggasoline-like polymers than can be obtained by the use of unmitigatedstrong acid.

Where the refinery gases employed have contained small amounts ofsulfur, the polymers obtained have manifested a tendency toward arelatively high sulfur content, but we have experienced no difficulty intreating the latter by simply washing the polymer with dilute alkalisolution. Wherever sulfur is present in the original gas in such formthat the polymers would contain sulfur in a form difficult to remove byordinary methods, the gases may be subjected to a simple desulfurizationtreatment in any'well known manner before being brought into contactwith the polymerizing catalyst.

In order to increase the yield of polymers, the gases are passed througha series of reactors containing the mitigated acid, preferably supportedupon an inert carrier as described. Recycling is not ordinarilydesirable unless the original gases consist predominantly ofpolymerizable olefins.

It may be observed that at the higher temperatures, and when the gasesare dry, the acid mixture may tend to lose moisture and become moreconcentrated. In continuous operation, this effect is 'readily overcomeby adding sufficient moisture, either to the acid or to the gases, tobalance the dehydrating effect and maintain the acid at the desiredconcentration.

While our invention has been described hereinabove with reference to thepolymerization of a particular butane cut, it will be obvious that otherrefinery gases and other olefinic gases in general may be employed asstarting materials, in so far as they contain substantial quantities ofpolymerizable olefin constituents. Moreover, while our invention hasbeen described in connection with its preferred embodiment, that is thestraight polymerization of gaseous olefins to liquid polymers useful asmotor fuels, the mixture of strong acid and mitigating agent may beemployed in other reactions, for example certain condensation reactions,in which sulfuric acid is contacted with olefins for the purpose ofproducing products of higher complexity by polymerization orcondensation and where it is desired to eliminate or reduce theundesirable decomposition reactions proportions of highand low-boilingpolymers I formed.

For example, wehave found that in polymerizing iso-butylene with benzenesulfonic acid containing 15 per cent by weight of boric acid, an

increase in the temperature of operation results in a much higher yieldof low-boiling polymers and vice versa, as indicated by the followingcomparative results:

Temperature ..C.. 8 2 l2l Pressure Atmospheric Atmospheric Distillationcharacteristics of polymers:

Up to 140 C .percent.. 19. 2 50. 0 140 C. to,200 0.... ....do. 69.1 34.0 Above 200 C ..d0. 12. 7 16.0

Consequently, when it is desired to manufacture relatively high-boilingpolymers, a relatively low temperature not exceeding, say, 100 C. shouldbe employed.

It will be apparent to those skilled in the art that. whereas ourinvention has been described hereinabove in connection with variousspecific operating details by way of example, our invention is not inits broadest aspects limited to such operating details, but may bevariously practiced within the scope of the claims hereinafter made.

What we claim is:

1. In a process of forming valuable compounds of higher molecular weightfrom normally gaseous oiefins under the influence of a strong acidcatalyst of the class consisting of sulphuric and sulphonic acids, theimprovement which comprises effecting contact between the olefinicstarting material and the strong acid catalyst in the 3. The process ofmaking liquid polymers from olefins of the class comprising propyleneand butylenes, which comprises subjecting such olefinic material tocontact with a mixture of a strong acid of the class consisting ofsulphuric and sulphonic acids and boric acid, the boric acid beingpresent in an amount sufficient to inhibit non-polymerizing action ofthe strong acid upon the hydrocarbon, at a temperature sufficiently highto cause the resultant polymers to vaporize, and condensing saidpolymers.

4. A process as set forth in claim 2 wherein the strong acid is to percent sulfuric acid.

5. A process as set forth in claim 3 wherein the boric acid is presentin an amount equal to from 10 to 25 per cent by weight of the strongacid.

6.A'process as set forth in claim 2 wherein the strong acid is benzenesulfonic acid.

7. The process of making liquid polymers from olefins of the classcomprising propylene and butylenes, which comprises passing a stream ofolefinic gas over an inert carrier impregnated with a mixture of 80 to90 per cent sulfuric acid and boric acid, the boric .acid. being presentin an amount sufficient to inhibit non-polymerizing action of the strongacid upon the hydrocarbon, at a temperature not exceeding 200 C., andcondensing the stream ofgas leaving the catalyst toremove resultantgasoline-like polymers therefrom.

8. The process of making liquid polymers use: ful as a safety fuel andcontaining a relatively high proportion of constituents boiling from 140C. to 200 C. from olefins' of the class comprising propylene andbutylenes, which comprises passing a stream of olefinic -gas intocontact with a mixture of a strong acid of the class consistin ofsulphuric and sulphonic acids and boric acid at a temperature notexceeding C. and removing the normally liquid polymers thereby obtained9. As a catalyst for the polymerization of olefins, a mixture of strongacid of the class consisting of sulphuric and sulphonic acids and anamount of boric acid suflicient to inhibit nonpolymerizing action of thestrong acid .on the olefins.

, 10. As a catalyst for the polymerization of oleflns, a mixture of 100parts by weight of 80 to 90 per cent sulfuric acid and from 10 to 25parts by weight of boric acid.

11. As a catalyst for the polymerization of olefins, a mixture ofbenzene sulfonic acid and an amount of boric acid suflicient to inhibitthe non-polymerizing action of the benzene sulfonic acid on the olefins.

12. A process as set forth in claim 2 wherein the v strong acid is aphenol sulfonic acid.

13. A process of producing a hydrocarbon product boiling within thegasoline range comprising contacting a mixture consisting predominantlyof C4 olefins and parafiins with a mixture of a strong acid selectedfrom the group consisting of sulfuric and sulfonic acids, with 10 to 25per cent by weight of boric acid.

DONALD R. STEVENS. WILLIAM A. GRUSE.

